Impulse relay

ABSTRACT

An impulse relay is formed by a U-shaped frame structure carrying a coil unit on the central wall thereof. A cam follower and contact-carrying arm sub-assembly is carried on a first transverse end wall and a cam and ratchet wheel sub-assembly is carried on an opposite confronting transverse end wall. An armature is pivoted on the first transverse end wall and spring urged away from the outer end of the coil unit. The armature extends in a space between the cam and ratchet wheel sub-assembly and terminates in transverse extensions which form pawl carrying and locking dog-forming portions which engage portions of the cam and ratchet wheels sub-assembly. The pawl carrying extension of the armature carries a flexibily mounted member from which extends pawl and locking dog-forming extensions which engage portions of the cam and ratchet wheel sub-assembly.

United States Patent 1 Williamson IMPULSE RELAY [75] Inventor: Harold L.Williamson, Arlington [211 App]. No.: 502,038

[52] U.S. Cl 335/140; 335/123 [51] Int. Cl. HOIH 51/08 [58] Field ofSearch 335/140, 123; 339/221 M [56] References Cited UNITED STATESPATENTS 3,115,563 12/1963 Tomaro, Jr. 335/123 3,204,062 8/1965 Foster etal.... 335/123 3,207,873 9/1965 Slonneger 335/123 3,412,350 11/1968Carli 335/1-23 3,533,054 10/1970 Spriggs et a] 339/221 M PrimaryExaminerI-larold Broome Attorney, Agent, or Firm-Wallenstein,Spangenberg, l-lattis & Strampel.

[ Oct. 21, 1975 [57] ABSTRACT An impulse relay is formed by a U-shapedframe structure carrying a coil unit on the central wall thereof. A camfollower and contact-carrying arm sub-assembly is carried on a firsttransverse end wall and a cam and ratchet wheel sub-assembly is carriedon an opposite confronting transverse end wall. An armature is pivotedon the first transverse end wall and spring urged away from the outerend of the coil unit. The armature extends in a space between the camand ratchet wheel sub-assembly and terminates in transverse extensionswhich form pawl carrying and locking dogforming portions which engageportions of the cam and ratchet wheels subassembly The pawl carryingextension of the armature carries a flexibily mounted member from whichextends pawl and locking dogforming extensions which engage portions ofthe cam and ratchet wheel sub-assembly.

10 Claims, 12 Drawing Figures US. Patent Oct. 21, 1975 Sheetlof23,914,725

RIG-5 FIG. 6'

US. Patent Oct. 21, 1975 Sheet 2 of2 3,914,725

FIG. .9 16.10

IMPULSE RELAY BACKGROUND OF THE INVENTION K contacts as the cams arerotated given incremental angular amounts. The cams are rotated in stepsby a ratchet wheel ganged thereto and engaged by an armature operatingpawl movable toward and away from the ratchet wheel by the movement ofthe armature toward and away from the coil unit. As the coil unitreceives successive impulses one or more cams are rotated givenincremental amounts to sequentially open or close one or more contacts.Such an impulse relay, for example, has utility in garage door openersand other electrical applications where successive pulses are toalternately open and close contacts to energize and de-energize electricmotors and other operating devices.

Prior impulse relays have left much to be desired from the standpoint ofcompactness, the number'of parts used therein and the ease of assemblythereof.

It is an object of the present invention to provide an impulse relayconstruction of minimum compactness and number of parts. A relatedobject of the invention is to provide an impulse relay as describedwhich is sturdy and therefore reliable in operation for an indefiniteperiod. A further object of the invention is to provide an impulse relayas described where the sub components thereof are so designed that theycan be quickly and easily assembled into a completed impulse relay,preferably without the use of screws and rivets.

SUMMARY OF THE INVENTION In accordance with one of the features of thepresent invention, the impulse relay comprises a frame having a centralwall upon which a coil unit is supported, and confronting transverse endwalls one of which carries a cam follower and contact carrying armsub-assembly with the arms thereof extending generally in a directionparallel to the coil unit support wall. The other transverse end wallcarrier a cam and ratchet wheel subassembly mounted for rotation aboutan axis extending in a plane generally parallel to the central andtransverse end walls. The cam and ratchet wheel subassembly is locatedbeyond the end of the coil unit facing away from the coil unitsupporting wall and in confronting relationship to the edge portion ofthe core unit remote from the side thereof nearest the transverse endwall carrying the cam follower and arm subassembly. This placement ofthe cam and ratchet wheel sub-assembly produces a reduced overall widthof the impulse relay in comparison to prior impulse relay constructionswhere, because of the relationship of the coil unit armature to suchsub-assembly, it was located completely to one side of the coil unit.This unique placement of the cam and ratchet sub-assembly is madepossible by an armature design which includes a main body portion whichis most advantageously pivoted upon the transverse end wall carrying thecam follower and contact carrying arm sub-assembly and extends beyondthe outer end of the coil unit and then passes in the space between thecam and ratchet wheel subassembly and the coil unit where it terminatesin transversely outwardly extending pawl carrying and lockingdog-forming portions. When the coil unit is deenergized, the lockingdog-forming portion thereof engages one of a number of flats on theperiphery of a locking dog wheel forming part of the cam and ratchetwheel sub-assembly. The pawl carrying armature portion has attachedthereto a flexibly mounted member from which extends a pawl which whenthe coil unit is energized, engages a ratchet wheel on the lattersubassembly, and an overshoot preventing dog which engages the ratchetwheel after the pawl has moved the ratchet wheel a given angular amount.

.In accordance with another feature of the invention, the cam andratchet wheel sub-assembly is preferably made of one or more partsinterconnected so that they are normally spring urged into an axiallyoutermost position, and are axially collapsable to permit readyinsertion between a pair of aperture pivot-forming ears extending fromone of the transverse end walls of the frame. Removal of the collapsingpressure on the subassembly after proper positioning thereof between thepivot-forming ears automatically results in its proper rotatably mountedpositioning between the ears.

The above and other features and advantages of the invention will becomeapparent upon making reference to the specification to follow, theclaims and the drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan partly broken away view ofan impulse relay exemplifying the most preferred form of the presentinvention;

FIG. 2 is a side elevational view of the impulse relay shown in FIG. 1;

FIG. 3 is an end elevational view of the impulse relay shown in FIGS. 1and 2;

FIG. 4 is an enlarged sectional view through the impulse relay shown inFIG. 2, taken along section line 4-4;

FIG. 5 is an enlarged plan view of the leaf spring used in the armatureassembly and in the cam and ratchet wheel assembly;

FIG. 6 is a sectional view through the spring of FIG. 5, taken alongsection line 6-6 therein;

FIG. 7 is a fragmentary enlarged central longitudinal sectional viewthrough the armature assembly and the cam and ratchet wheel assembly,showing the relative positions of the pawl and overshoot preventing dogwhen the coil unit is deenergized;

FIG. 8 is a view corresponding to FIG. 7 when the coil unit isenergized;

FIG. 9 is a plan view of the cam and ratchet wheel assembly before beinginstalled in the frame of the impulse relay;

FIG. 10 is a transverse sectional view through the assembly of FIG. 9,taken along section line l0l0;

FIG. 11 is a longitudinal sectional view through the cam and ratchetwheel assembly of FIG. 9, taken along section line 11-11; and

FIG. 12 is a perspective view of the armature assembly.

DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION The impulserelay shown in the drawings comprises a frame and coil unit sub-assemblyA, an armature, pawl and locking dog sub-assembly B, a cam and ratchetwheel sub-assembly C and a cam follower and contact carryingsub-assembly D. The frame and coil unit assembly A includes a generallyU-shaped frame 2 having a main or central support wall 2a from theopposite ends of which transversely extend spaced confronting end walls21) and 2c. Struck from the end wall 2b is a tab 2b extendingtransversely of the end wall 2b. The upper end of the end wall 2bterminates in a pair of mounting ears 2b"2b which pass through openingsin a housing 3 of the cam follower and contact-carrying sub-assembly Dwhere the ends thereof are staked'to anchor the housing 3 in placethereon. The transverse end wall 2c terminates at the top thereof inpivotforming ears 2c'-2c" which rotatably mount the cam and ratchetwheel sub-assembly C about an axis parallel to the main and transverseframe end walls 2a, 2b and 2c in a manner to be described. The end wall2b includes an armature-receiving aperture 10 (FIG. 3) having a roundedarmature pivot-forming edge 11 at the inner margin thereof. The aperture10 is interrupted by wall extensions 13-13 which form narrow aperturesections la-l0a within'which the armature portion of the armature pawland locking dog assembly B extend in a manner to be described.

The central wall 2a of the frame 2 supports on the inner face thereof acoil unit 5 including a housing 6 made of synthetic plastic material,the housing including a cylindrical section 6a within which a coilwinding (not shown)- and a core 8 are located, and a housing section 6bfrom which extend terminals 9-9 which electrically connect to the endsof the coil winding within the housing section 6. The coil unit 5 may beheld in place upon the main wall 2a in any suitable way, such as bystaking the core 8 in place within a countersunk opening 7 within thecentral wall 2a of the frame. The core may be threaded at this point toreceive a screw of anchoring the impulse relay on a support panel or thelike.

The armature, pawl and locking dog sub-assembly B includes a metalarmature 20 having a main body portion 20a pivoted within thearmature-receiving recess 10 in the end wall 2b of the frame 2. The mainbody portion a of the armature 20 pivots on the aforementionedpivot-forming edge 11 of the frame end wall 2b. The main body portion20a of the armature terminates in a generally T-shaped extension 24(FIG. 4 formed by narrow slots 24a-24a forming a neck portion having awidth equal to the length of the armature receiving aperture 10. Thearmature interlocks with the defining walls of the bottom portion of thearmature receiving aperture 10 in a way where the armature can pivot upand down over the edge 11, but is otherwise held in place within theaperture 10 by the defining walls of the apertures 10a-l0a. A coilspring 12 has an end 12b hooked around a recessed portion 14 (FIG. 2) ofthe tab 2b and an end 12a which hooks around an indented portion 18 atthe knobbed end 24b of the T shaped extension 24 of the armature. Thespring 12 biases the armature 20 so that the main body portion 20ainclines away from the outer end of the coil unit 6 as illustrated inFIG. 2 when the coil unit is de-energized. The outward movement of thearmature is limited by the engagement of an abutment projection 22struck from the main body portion 20a of the armature 20 with the innerface of the housing 3 of the cam follower and contact-carrying armsub-assembly D.

The main body portion 20a of the armature terminates in a pair of aL-shaped extensions 21 and 23. The extension 21 has a portion 21aextending in the space between the cam and ratchet wheel assembly C andthe coil unit 5, and a transversely outwardly extending end portion 21b.The transverse end portion 21b has flexibly secured thereto a moldedsynthetic plastic member 27 having an inverted L-shaped portion 27adefining a pawl-forming projection 31 and an overshoot preventingdog-forming projection 30. The synthetic plastic member 27 has arearwardly extending shank passing loosely through an opening 35 in thetransversely extending end portion 21b of the armature which shankportion is anchored in place in any suitable way to the armature, as bya locking washer 34. A leaf spring 32 positioned between the inner faceof the transversely extending end portion 21b of the armature and a headportion 27b of the synthetic plastic member 27 so as to permit themember 27 to flex in a plane transverse to the axis of rotation of thecam and ratchet wheel sub-v assembly C, to permit the pawl projections31 to clear the teeth of the ratchet wheel to be described. While thespring 32 may take a variety of forms, as illustrated it is an arcurateshaped member having a central square opening 36 received over thesimilarly shaped shank portion 33 of the synthetic plastic member 27 andend apertures 34-34, one of which stradles a projection 270 of thesynthetic plastic member 27.

The armature extension 23 has an inner end portion 23a which passes inthe space between the cam and ratchet wheel sub-assembly C and the coilunit 5, and

a transversely outwardly extending end portion 23b which forms a lockingdog in a manner to be described.

The preferred cam and ratchet wheel sub-assembly C is a collapsibleassembly including a centrally disposed ratchet wheel-forming part 40preferably made of a molded synthetic plastic material and having axialextensions 42-42 preferably of square cross section slidably receivedwithin correspondingly shaped apertures 43-43 in a pair of outercam-forming parts 41-41 also preferably made of molded synthetic plasticmaterial. Sandwiched between the confronting end faces of the ratchetwheel-forming part 40 and each of the cam forming parts 41-41 are springmeans such as a leaf spring 32 previouslydescribed. The square shapedcenter apertures 36 of the leaf spring 32-32 are sized to fit over thecorrespondingly shaped axial extensions 42-42 of the ratchetwheel-forming part 40, the leaf springs urging these parts 40, 41 and41' axially outwardly. The cam-forming parts 41 and 41 respectively haveaxially aligned cylindrical extensions 41a-41a which fit withincorrespondingly shaped circular pivot-forming apertures 49-49 (FIG. 2)in the frame ears 2c-2c'. To mount the cam and ratchet wheelsub-assembly C between the ears 2c-2c', it is merely necessary to holdthe assembly in acollapsed state while placing the same so that thecylindrical extensions 4la-41a are in alignment with the frame earapertures 49-49. Upon release of the assembly collapsing pressure, theassembly expands outwardly into interlocking relationship with the frameears. In the process of collapsing the sub-assembly C, the axialextensions 42-42 of the ratchet wheel-forming part 40 slide furtherwithin the apertures 43-43 in the cam forming parts 41-41.

As best shown in FIGS. 7 and 8, the ratchet wheel forming part 40defines a ratchet wheel 44 having in the illustrated embodiment of theinvention 8 ratchet teeth 44a, each having a radially extending margin44a and a generally tangentially extending margin 44a". When the coilunit 5 is energized and the armature is drawn against the core of thecoil unit, the pawlforming projection 31 of the armature carried member27 engages the radially extending margin 44a of one of the ratchet teeth44a to impart a given amount of angular rotation equal to one-eighth ofa revolution in the example illustrated when the armature reaches itsposition adjacent the core of the coil unit. The overshoot preventingprojection 30 of the armature carried member 27 engages the tangentiallyextending margin 44a" of one of the ratchet teeth, as shown in FIG. 8,after the ratchet wheel rotates one-eighth of a revolution to preventovershoot thereof. The coil unit is operated only be a momentary currentpulse, and upon termination of this pulse the spring 12 will return thearmature to its normal outermost position shown in FIG. 7. As thearmature starts to return to its initial position, the locking dog 23bon the armature extension 23 engages a part of the sub-assembly C to bedescribed to prevent movement thereof, and the flexibly mounted member27 flexes to permit the pawl projection 31 to slip by the ratchet wheeltooth 44a.

The cam-forming part 41, in addition to forming a cam 48 to bedescribed, also forms a locking dog wheel 46 which has the identicalsize and shape as the ratchet wheel 44 except that the teeth 46a thereof(FIG. project in the opposite direction. Also, when the coil unit isde-energized, the circumferentially extending margin 46a of one of theteeth thereof is engaged by the locking dog 23b of the armatureextension 23 to lock the cam and ratchet wheel sub-assembly againstrotation.

The cam-forming parts 41 and 41 form cams 48 and 48'. Refer now to FIG.10 which also illustrates the configuration of the cam 48, it beingunderstood that the configuration of the cam 48' is identical theretoexcept for a slightly different angular orientation. Corresponding partsthereof are similarly numbered except a prime has been added to thenumber identifying the part of cam 48. The cam 48 has four lobes 50,each of which includes an outermost cam arm engageable portion 52 and aflat 54 positioned at a closer distance to the center of the cam thanthe outermost portion 52. In the illustrated embodiment of theinvention, when the coil unit 5 is de-energized, the cams 48 and 48 havesuch different angular positions that the outermost cam engaging portion52 or 52 of one of the lobes of the cam 48 or 48 faces outwardly to beengaged by a cam follower portion 62a or 70a of a contact carrying arm62 or 70, while the flat 54 or 54' of one of the lobes of the other cam48' or 48 faces outwardly where it is engaged by the camfollower-forming extension 70a or 62a of the contact-carrying arm 70 or62. The arms 62 and 70 are anchored within the housing 3 in a manner tobe described.

The arm 62 carries on one side thereof a contact 62' which, as shown inFIG. 8, respectively makes engagement with a stationary contact 64' onan arm 64 when the cam follower-forming extension 62a rides upon theoutermost section 52' of the lobe of the cam 48'. The arm carries acontact 62" which makes contact with a stationary contact 66' on acontact carrying arm 66 when the cam follower portion 62a of the arm 62rides on a lobe flat 54 of the associated cam 48.

The aforementioned arm carries a contact 70 which is spaced from astationary contact 68' on a contact carrying arm 68 when the camfollowerforming extension 70a rides on a flat 54 ofa lobe 50 of the cam48, and makes engagement with a stationary contact 68 when the camfollower-forming extension 70a rides upon the outermost portion 52 ofone of the lobes 50 of the cam 48. Of course, the particular contactarrangement for the relay can vary widely, depending upon the needs ofthe electrical circuit in which the relay is placed. Thus, there can beeither one or two stationary contacts associated with each camfollower-forming arm.

The various contact carrying arms 62, 64, 66, 68, and 70 respectivelypass through aperture 3a, 3b, 3c, 3d, and 3e in the housing 3, wherethey terminate in exposed soldering terminals 62b, 64a, 66a, 68b and70a70a.

Another unique aspect of the impulse relay illustrated is the manner inwhich the various arms 60, 64, 66, etc. are anchored within the housing3. As best illustrated in FIG. 1, the portion of the various armsreferred to which extend through the housing 3 have barbed contours like67 along both longitudinal edges thereof so as to bite into thesynthetic plastic material lining the sides of the various apertures 3a,3b, 3c, 3d and 3e formed in the housing to receive these arms.Manifestly, the widths of the arms is slightly greater than thecorresponding dimension of these apertures, so that they can be anchoredin place by merely force fitting the same within these apertures.

It should be apparent that the present impulse relay has the advantageof maximum compactness because of the relationship of the armature 20,and the extensions 21 and 23 thereof with respect to the cam and ratchetwheel sub-assembly C. It is made of a minimum number of parts because ofthe manner in which the various operating portions thereof, such as thepawl 31 and the dogs 30 and 23b, are formed and located. Moreover, thecollapsible construction of the cam and ratchet wheel sub-assemblyCcontributes to the low cost and ease of assembly of the impulse relay.

It should be understood that numerous modifications may be made in themost preferred form of the invention described above without deviatingfrom the broader aspects of the invention.

1 claim:

1. An impulse relay including a coil unit, cam follower andcontact-carrying arms, an armature spring urged outwardly away from theouter end of the coil unit so upon energization of the coil unit thearmature is drawn toward the coil unit against the restraining force ofthe spring, a cam and ratchet wheel assembly mounted for rotation abouta common axis and located outwardly of the coil unit, said armaturehaving portions extending in the space between the cam and ratchet wheelassembly, on the one hand, and said coil unit on the other hand, andterminating in transversely outwardly extending pawl carrying portion,said pawl carrying portion including a pawl-forming extension projectingtoward the outer side of said cam and ratchet wheel assembly, said camand ratchet wheel assembly including cam means and ratchet wheel means,said ratchet wheel means being engaged by said pawlforming extensionwhen said coil unit is energized, and when said coil unit is energizedsaid cam means being engaged by said cam follower arms to effect openingand/or closing of contacts carried thereby as said cam and ratchet wheelassembly is rotated, said armature also having atransver'sel'y outwardlyextending locking dog-forming portion which, when the coil unit isdeenergized, engages a portion of the cam and ratchet wheel sub-assemblyto hold the same against rotation until'the pawl is drawn to said coilunit, said pawlforming extension being formed on a member flexiblysecured to said pawl carrying portion of said armature, said memberincluding in addition to said pawl-forming extension an overshootpreventing dog-forming extension projecting towards said cam and ratchetwheel sub-assembly on the outer side thereof, said overshoot preventingthe dog-forming extension engaging a portion of said cam and ratchetwheel assembly to stop further rotation thereof after a given amount ofrotation is imparted to the ratchet wheel means by said pawlformingextension upon energization of the coil unit.

2. The impulse relay of claim 1 wherein said armature also has atransversely outwardly extending locking dog-forming portion which, whenthe coil unit is deenergized, engages a portion of the cam and ratchetwheel sub-assembly to hold the same against rotation until the pawl isdrawn to said coil unit.

The impulse relay of claim 1 wherein said pawlforming extension isformed on a member flexibly secured to said pawl carrying portion ofsaid armature, saidmember including in addition to said pawl-formingextension an overshoot preventing dog-forming extension projectingtowards said cam and ratchet wheel sub-assembly on the outer sidethereof, said overshoot preventing dog-forming extension engaging aportion of said cam and ratchet wheel assembly to stop further rotationthereof.

4. The impulse relay of claim 1 wherein said cam and ratchet wheelassembly confronts the marginal end portion of the coil unit on the sidethereof where said transversely outwardly extending pawl-carryingportion of the armature is located.

5. An impulse relay comprising a frame having a main support wall onwhich a coil unit is supported and from which outwardly extend a pair ofspaced confronting transversely extending end walls, a cam follower andcontact-carrying arm sub-assembly mounted on one of said transverselyextending end walls and having contact carrying and cam follower-formingarms extending in the direction of the other transversely extending endwall, an armature mounted on said one transversely extending end walland spring urged away from the outer end of the coil unit so uponenergization of the coil unit the armature is drawn toward the coil unitagainst the restraining force of the spring, a cam and ratchet wheelsub-assembly mounted on said other transversely extending end wall andfor rotation about an axis extending generally parallel to said main andtransversely extending walls, and located beyond the outer end of thecoil unit in a direction parallel to said transversely extending endwalls, said armature having portions extending in the space between thecam and ratchet wheel sub-assembly, on the one hand, and said coil unit,on the other hand, and terminating in a transversely extending pawlcarrying portion, said pawl carrying portion carrying a pwalformingextension projecting toward said cam and ratchet wheel sub-assembly onthe side thereof remote from said main support wall, said cam andratchet wheel sub-assembly including cam means and ratchet wheel meansengaged by said pawl-forming extension when said coil unit is energized,said cam means being engaged by said cam follower-forming arms of saidfollower and contact carrying arm assembly when said coil unit isenergized to effect opening and closing of contacts carried thereby assaid cam and ratchet wheel assembly is rotated, said armature alsohaving a transversely outwardly extending locking dog-forming portionwhich when the coil unit is deenergized engages a portion of the cam andratchet wheel sub-assembly to hold the same against rotation until thepawl is drawn to said coil unit, and said pawl-forming extension beingformed on a member flexibly secured to said pawl carrying portion ofsaid armature, said member including in addition to said pawl-formingextension an overshoot preventing dog-forming extension projectingtowards said cam and ratchet wheel sub-assembly on the outer sidethereof, said overshoot preventing dog-forming extension engaging aportion of said cam and ratchet wheel assembly to stop further rotationthereof after a given amount of rotation is imparted to the ratchetwheel means by said pawl-forming extension upon energization of the coilunit.

6. An impulse relay comprisingia frame having a main support wall onwhich a coil unit is supported and from which outwardly extend a pair ofspaced confronting transversely extending end walls, a cam follower andcontact-carrying arm sub-assembly mounted on one of said transverselyextending end walls and having contact carrying and cam follower-formingarms extending in the direction of the other transversely extending endwall; an armature mounted on said one transversely extending end walland spring urged away from the outer end of the coil unit soenergization of the coil unit the armature is drawn toward the coil unitagainst the restraining force of the spring; a cam and ratchet wheelsub-assembly mounted on said other transversely extending end wall andfor rotation about an axis extending generally parallel to said main andtransversely extending walls, and located beyond the outer end of thecoil unit in a direction parallel to said transversely extending endwalls, said armature having portions extending in the space between thecam and ratchet wheel sub-assembly, on the one hand, and said coil unit,on the other hand, and terminating in transversely extending pawlcarrying and locking dog-forming portions, said pawl carrying portionhaving secured thereto a flexibly mounted member having a firstpawl-forming extension projecting toward said cam and ratchet wheelsub-assembly on the side thereof remote from said main support wall andan overshoot preventing dog-forming extension projecting toward said camand ratchet wheel assembly on the latter said of the assembly; said camand ratchet wheel sub-assembly including cam means, ratchet wheel meansand locking dog wheel means, said ratchet wheel means being engaged bysaid pawl-forming extension when said coil unit is energized, and bysaid overshoot preventing dog-forming extension when said coil unit isenergized after a given amount of rotation is imparted to the ratchetwheel means, said locking dog wheel means being engaged and held by saidlocking dogforming portion of said armature when said coil unit isdeenergized, and said cam means being engaged by said camfollower-forming arms of said follower and contact carrying armsub-assembly when said coil unit is energized to effect opening andclosing of contacts carried thereby as said cam and ratchet wheelassembly is rotated.

7. In an impulse relay including a coil unit, an annature movable towardand away from the coil unit as the latter is energized and de-energized,cam follower and contact-carrying arm means for effecting contactopening and closing operations when said coil unit is energized and/orde-energized, an assembly of rotatably mounted cam means upon which thecam follower arm means ride and rotatably mounted ratchet wheel meansengagable by a pawl operated by said armature to effect incrementalrotation of said cam means, the improvement in the support andarrangement of said ratchet wheel means and cam means comprising spacedconfronting bearing-forming walls providing a rotatable support for saidratchet wheel means and cam means, said ratchet wheel means and cammeans being formed by at least two separate members mounted together forrelative axial movement and rotation about a common axis, spring meansurging the ratchet wheels and cam-forming members axially apart wherethey are collapsible against the restraining force of said spring meansto reduce the overall axial extend thereof, said spring urged assemblyof said cam and ratchet wheelforming members when in a collapsedcondition being insertable between said confronting bearing-formingmembers, said cam and ratchet wheel-forming members and said confrontingpivot-forming members having means which telescopingly engage when thecollapsing pressure on said assembly is removed and said members assumetheir outermost positions relative to one another.

8. The impulse relay of claim 7 wherein one of said members of saidassembly is an axially extending projection slidably received within aslot in the other of same, so that when the assembly is in its collapsedcondition said axially extending projection extends to a greater degreewithin said slot.

9. The impulse relay of claim 7 wherein said assembly of said cam andratchet-forming members comprise a central ratchet wheel-forming memberpositioned between a pair of outermost cam-forming members, said centralratchet wheel-forming member having means interconnecting with each ofsaid cam-forming members to permit relatively axial movementtherebetween, said spring means urging said ratchet wheel-forming memberand each of said cam-forming members apart and permitting the collapsingof the assembly to reduce the overall axial extent of the assembly toenable the insertion thereof between said bearing-forming members.

10. The impulse relay of claim 9 wherein there is formed as an integralpart of one of said cam-forming members a locking wheel against which alocking dog is urged to hold the same against rotation when the coilunit is in a de-energized state, said locking dog being withdrawn fromsaid locking where when the coil unit is energized.

1. An impulse relay including a coil unit, cam follower andcontact-carrying arms, an armature spring urged outwardly away from theouter end of the coil unit so upon energization of the coil unit thearmature is drawn toward the coil unit against the restraining force ofthe spring, a cam and ratchet wheel assembly mounted for rotation abouta common axis and located outwardly of the coil unit, said armaturehaving portions extending in the space between the cam and ratchet wheelassembly, on the one hand, and said coil unit on the other hand, andterminating in transversely outwardly extending pawl carrying portion,said pawl carrying portion including a pawl-forming extension projectingtoward the outer side of said cam and ratchet wheel assembly, said camand ratchet wheel assembly including cam means and ratchet wheel means,said ratchet wheel means being engaged by said pawl-forming extensionwhen said coil unit is energized, and when said coil unit is energizedsaid cam means being engaged by said cam follower arms to effect openingand/or closing of contacts carried thereby as said cam and ratchet wheelassembly is rotated, said armature also having a transversely outwardlyextending locking dog-forming portion which, when the coil unit isde-energized, engages a portion of the cam and ratchet wheelsub-assembly to hold the same against rotation until the pawl is drawnto said coil unit, said pawl-forming extension being formed on a memberflexibly secured to said pawl carrying portion of said armature, saidmember including in addition to said pawlforming extension an overshootpreventing dog-forming extension projecting towards said cam and ratchetwheel sub-assembly on the outer side thereof, said overshoot preventingthe dog-forming extension engaging a portion of said cam and ratchetwheel assembly to stop further rotation thereof after a given amount ofrotation is imparted to the ratchet wheel means by said pawlformingextension upon energization of the coil unit.
 2. The impulse relay ofclaim 1 wherein said armature also has a transversely outwardlyextending locking dog-forming portion which, then the coil unit isde-energized, engages a portion of the cam and ratchet wheelsub-assembly to hold the same against rotation until the pawl is drawnto said coil unit.
 3. The impulse relay of claim 1 wherein saidpawl-forming extension is formed on a member flexibly secured to saidpawl carrying portion of said armature, said member including inaddition to said pawl-forming Extension an overshoot preventingdog-forming extension projecting towards said cam and ratchet wheelsub-assembly on the outer side thereof, said overshoot preventingdog-forming extension engaging a portion of said cam and ratchet wheelassembly to stop further rotation thereof.
 4. The impulse relay of claim1 wherein said cam and ratchet wheel assembly confronts the marginal endportion of the coil unit on the side thereof where said transverselyoutwardly extending pawl-carrying portion of the armature is located. 5.An impulse relay comprising a frame having a main support wall on whicha coil unit is supported and from which outwardly extend a pair ofspaced confronting transversely extending end walls, a cam follower andcontact-carrying arm sub-assembly mounted on one of said transverselyextending end walls and having contact carrying and cam follower-formingarms extending in the direction of the other transversely extending endwall, an armature mounted on said one transversely extending end walland spring urged away from the outer end of the coil unit so uponenergization of the coil unit the armature is drawn toward the coil unitagainst the restraining force of the spring, a cam and ratchet wheelsub-assembly mounted on said other transversely extending end wall andfor rotation about an axis extending generally parallel to said main andtransversely extending walls, and located beyond the outer end of thecoil unit in a direction parallel to said transversely extending endwalls, said armature having portions extending in the space between thecam and ratchet wheel sub-assembly, on the one hand, and said coil unit,on the other hand, and terminating in a transversely extending pawlcarrying portion, said pawl carrying portion carrying a pwal-formingextension projecting toward said cam and ratchet wheel sub-assembly onthe side thereof remote from said main support wall, said cam andratchet wheel sub-assembly including cam means and ratchet wheel meansengaged by said pawl-forming extension when said coil unit is energized,said cam means being engaged by said cam follower-forming arms of saidfollower and contact carrying arm assembly when said coil unit isenergized to effect opening and closing of contacts carried thereby assaid cam and ratchet wheel assembly is rotated, said armature alsohaving a transversely outwardly extending locking dog-forming portionwhich when the coil unit is deenergized engages a portion of the cam andratchet wheel sub-assembly to hold the same against rotation until thepawl is drawn to said coil unit, and said pawl-forming extension beingformed on a member flexibly secured to said pawl carrying portion ofsaid armature, said member including in addition to said pawl-formingextension an overshoot preventing dog-forming extension projectingtowards said cam and ratchet wheel sub-assembly on the outer sidethereof, said overshoot preventing dog-forming extension engaging aportion of said cam and ratchet wheel assembly to stop further rotationthereof after a given amount of rotation is imparted to the ratchetwheel means by said pawl-forming extension upon energization of the coilunit.
 6. An impulse relay comprising a frame having a main support wallon which a coil unit is supported and from which outwardly extend a pairof spaced confronting transversely extending end walls, a cam followerand contact-carrying arm sub-assembly mounted on one of saidtransversely extending end walls and having contact carrying and camfollower-forming arms extending in the direction of the othertransversely extending end wall; an armature mounted on said onetransversely extending end wall and spring urged away from the outer endof the coil unit so energization of the coil unit the armature is drawntoward the coil unit against the restraining force of the spring; a camand ratchet wheel sub-assembly mounted on said other transverselyextending end wall and for rotation about an axis extending generallyparallel tO said main and transversely extending walls, and locatedbeyond the outer end of the coil unit in a direction parallel to saidtransversely extending end walls, said armature having portionsextending in the space between the cam and ratchet wheel sub-assembly,on the one hand, and said coil unit, on the other hand, and terminatingin transversely extending pawl carrying and locking dog-formingportions, said pawl carrying portion having secured thereto a flexiblymounted member having a first pawl-forming extension projecting towardsaid cam and ratchet wheel sub-assembly on the side thereof remote fromsaid main support wall and an overshoot preventing dog-forming extensionprojecting toward said cam and ratchet wheel assembly on the latter saidof the assembly; said cam and ratchet wheel sub-assembly including cammeans, ratchet wheel means and locking dog wheel means, said ratchetwheel means being engaged by said pawl-forming extension when said coilunit is energized, and by said overshoot preventing dog-formingextension when said coil unit is energized after a given amount ofrotation is imparted to the ratchet wheel means, said locking dog wheelmeans being engaged and held by said locking dog-forming portion of saidarmature when said coil unit is deenergized, and said cam means beingengaged by said cam follower-forming arms of said follower and contactcarrying arm sub-assembly when said coil unit is energized to effectopening and closing of contacts carried thereby as said cam and ratchetwheel assembly is rotated.
 7. In an impulse relay including a coil unit,an armature movable toward and away from the coil unit as the latter isenergized and de-energized, cam follower and contact-carrying arm meansfor effecting contact opening and closing operations when said coil unitis energized and/or de-energized, an assembly of rotatably mounted cammeans upon which the cam follower arm means ride and rotatably mountedratchet wheel means engagable by a pawl operated by said armature toeffect incremental rotation of said cam means, the improvement in thesupport and arrangement of said ratchet wheel means and cam meanscomprising spaced confronting bearing-forming walls providing arotatable support for said ratchet wheel means and cam means, saidratchet wheel means and cam means being formed by at least two separatemembers mounted together for relative axial movement and rotation abouta common axis, spring means urging the ratchet wheels and cam-formingmembers axially apart where they are collapsible against the restrainingforce of said spring means to reduce the overall axial extend thereof,said spring urged assembly of said cam and ratchet wheel-forming memberswhen in a collapsed condition being insertable between said confrontingbearing-forming members, said cam and ratchet wheel-forming members andsaid confronting pivot-forming members having means which telescopinglyengage when the collapsing pressure on said assembly is removed and saidmembers assume their outermost positions relative to one another.
 8. Theimpulse relay of claim 7 wherein one of said members of said assembly isan axially extending projection slidably received within a slot in theother of same, so that when the assembly is in its collapsed conditionsaid axially extending projection extends to a greater degree withinsaid slot.
 9. The impulse relay of claim 7 wherein said assembly of saidcam and ratchet-forming members comprise a central ratchet wheel-formingmember positioned between a pair of outermost cam-forming members, saidcentral ratchet wheel-forming member having means interconnecting witheach of said cam-forming members to permit relatively axial movementtherebetween, said spring means urging said ratchet wheel-forming memberand each of said cam-forming members apart and permitting the collapsingof the assembly to reduce the overall axial extent of the assembly toenable the insertion thereof between said bearing-forming members. 10.The impulse relay Of claim 9 wherein there is formed as an integral partof one of said cam-forming members a locking wheel against which alocking dog is urged to hold the same against rotation when the coilunit is in a de-energized state, said locking dog being withdrawn fromsaid locking where when the coil unit is energized.